Arthropods abound in our homes


In contrast to the caves used by early humans, today’s Western homes are perceived as environments devoid of animal life, except for our pets. However, as the pest control industry’s turnover demonstrates, arthropods thrive in our homes, and they do in great numbers and diversity too.

Since man was a sedentary animal, he has lived in the domestic environment with other unwanted organisms that come in search of food and shelter. Insects, spiders and their kin have lived and evolved with us throughout our history.

The most diverse and abundant group of multicellular life that can be found in homes today are represented by arthropods, and many of the species now associated with our homes were originally cave dwellers, such as bed bugs.

Despite this long coexistence, little is known about our arthropod hosts, with the exception of the main groups of pests, with medical or economic relevance, such as cockroaches, termites, bedbugs or mosquitoes.

The interaction between these non-target species and people, whether beneficial, neutral or negative, remains largely unknown, as does their prevalence and distribution.

A study carried out at the University of Carolina (USA) collects for the first time comprehensive data on the diversity of arthropods collected in isolated urban and suburban homes in the city of Raleigh, North Carolina. The results are surprising, both for the prevalence of animals and their diversity: from the 50 houses studied (554 rooms), more than 10,000 specimens were collected and identified, representing at least 579 species.

Six orders of arthropods dominated the households, representing 81% of the diversity in the average normal room: Diptera (flies) 23%, Coleoptera (beetles) 19%, Arachnids (spiders) 16%, Hymenoptera (predominantly ants) 15%, Psocoptera (lice of books) 4% and Hemiptera (insects) 4%.

Each house housed between 32 and 211 species of arthropods, whose presence varied according to the type of room; bathroom, kitchen, bedroom, etc. Of the more than 550 rooms studied, no arthropods were found in just five of them.

Among the more than 10,000 specimens collected, the four subphyla (Chelicerates, Myriapods, Crustaceans and Hexapods) were represented, in addition to six classes, 34 orders, 304 families of arthropods and at least 579 species.

The class of insects was found in 100% of the dwellings, being present, among others, several species of cockroaches (82% of the dwellings), silverfish (68%), crickets and grasshoppers (76%), various types of bedbugs (98%) and lice, mainly book lice (98%).

Hymenoptera were found in all houses, mainly ants (100%). None of them lacked beetles either, with the carpet beetle present in 100% of the houses and weevils in 82%. Moths and butterflies (lepidoptera) were in 92% of households and flies and mosquitoes, of various species, in 100%. Arachnids, in turn, appeared in 100% of the houses; spiders in 100% and mites in 76%, mainly dust mites. Millipedes or millipedes were also found in 82%.

In fact, the authors of the study calculate that the real quantity and diversity of arthropods in the houses studied is even greater than what was registered, since samples were not collected in areas behind walls, under heavy furniture, in drawers or cupboards, which undoubtedly are potential refuges for arthropods. The vast majority live with us peacefully and inadvertently and it is considered that they do not represent a hygiene, health or structural problem.

Typical household pests were not common and were found in a minority of homes, such as the German cockroach (Blatella germanica, 6% of homes), subterranean termites (Rhinotermitidae, 28%) and fleas (Pulicidae, 10%). Bedbugs (Cimex lectularius Linnaeus) were not found in the study and the American cockroach (Periplaneta americana) was found in only three homes.

The rich diversity of arthropods identified reflects a whole gradient of associations with human environments, from synanthropic arthropods strongly adapted to habitation (web spiders, carpet beetles or bookworms) to others that seek shelter and food only occasionally (ants, hunting spiders, beetles) and others who simply accidentally become trapped in houses and find a way out or do not survive.

The results of the study provide greater knowledge about the ecological dynamics of the biome within the residences. However, according to the authors, more research is needed to understand the potential health and economic implications of species that live and have evolved so close to us.

Source: Environmental Hygiene

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